A heat-recoverable article is an article the dimensional configuration of which may be made substantially to change when subjected to heat treatment. Usually these articles recover, on heating, towards an original shape from which they have previously been deformed, but the term "heat-recoverable", as used herein, also includes an article which, on heating, adopts a new configuration, even if it has not been previously deformed.
In their most common form, such articles comprise a heat-shrinkable sleeve made from a polymeric material exhibiting the property of elastic or plastic memory as described, for example, in U.S. Pat. Nos. 2,027,962; 3,086,242 and 3,597,372. As is made clear in, for example, U.S. Pat. No. 2,027,962, the original dimensionally heat-stable form may be a transient form in a continuous process in which, for example, an extruded tube is expanded, whilst hot, to a dimensionally heat-unstable form but, in other applications, a preformed dimensionally heat stable article is deformed to a dimensionally heat unstable form in a separate stage.
In other articles, an elastomeric member is held in a stretched state by a second member, which, upon heating weakens and thus allows the elastomeric member to recover. Heat-recoverable articles of this type are described, for example, in British Patent No. 1,440,524 in which an outer tubular elastomeric member is held in a stretched state by an inner tubular member.
Heat-recoverable articles have found particular use in the environmental protection of elongate substrates such as for example splices in telecommunication cables.
It has been proposed, in U.S. Pat. No. 3,669,157 to Carolina Narrow Fabric Company and in Japanese Pat. No. 53-13805 to Matsushita, to provide heat-shrinkable tubular fabric articles which may be impregnated with certain thermosetting resins. However, we have found that the articles disclosed therein are very difficult to install because they are subject to displacement of the resin on recovery, resulting in burst-through of fabric by the resin, or delamination of the resin from the fabric. Thus these prior art articles are of limited utility and are too craft-sensitive for use in most telecommunications applications.